Electrically conductive adhesive compositions

• US 5,362,421 A
• Filed: 06/16/1993
• Issued: 11/08/1994
• Est. Priority Date: 06/16/1993
• Status: Expired due to Term

• Current Assignee: Minnesota Mining and Manufacturing Co (3M Company), Carolyn V Peters
• Original Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Inventors: Mahoney, Wayne S., Kropp, Michael A.
• Primary Examiner(s): Zirker, Daniel R.
• Application Number:
  US08/078,740
• Time in Patent Office: 510 Days
• Field of Search: 556/47, 556/60, 556/142, 556/144, 525/56, 525/403, 525/420, 525/436, 525/437, 525/462, 525/535, 428/355, 428/352, 252/512, 252/514, 522/66, 522/126, 522/146
• US Class Current: 252/512
• CPC Class Codes: C08G 59/68 characterised by the catalysts used
• CPC Class Codes: C08L 2666/02 Organic macromolecular compounds, natural resins, waxes or and bituminous materials
• CPC Class Codes: C09J 163/00 Adhesives based on epoxy resins; Adhesives based on derivatives of epoxy resins
• CPC Class Codes: H05K 2201/0129 Thermoplastic polymer, e.g. auto-adhesive layer; Shaping of thermoplastic polymer
• CPC Class Codes: H05K 2201/0239 Coupling agent for particles
• CPC Class Codes: H05K 2203/121 Metallo-organic compounds
• CPC Class Codes: H05K 3/323 by applying an anisotropic conductive adhesive layer over an array of pads
• CPC Class Codes: Y10T 428/2839 with release or antistick coating
• CPC Class Codes: Y10T 428/2852 Adhesive compositions

Abstract

An anisotropically conductive adhesive composition provides electrical conductivity between facing electrodes but maintains electric insulation laterally between adjacent electrodes and comprises (a) a cationically polymerizable monomer, such as a glycidyl epoxy resin; (b) a thermoplastic resin, essentially free of nucleophilic or metal complexing functional groups; (c) optionally, an alcohol containing material; (d) a thermally initiated catalyst system comprising: (1) a salt of an organometallic cation; (2) a cure rate enhancer; and (3) a stabilizing additive; (e) conductive particles; and (f) optionally, a silane coupling agent, wherein the adhesive compositions cure at a temperature of 120°-125° C.

Claims

1. An anisotropically conductive adhesive curable composition comprising:

(a) at least one cationically curable epoxy resin;

(b) at least one thermoplastic resin essentially free of nucleophilic or metal complexing functional groups;

(c) a multi-component thermal initiator comprising;

(1) at least one salt of an organometallic complex cation wherein the organometallic cation is selected from a class of substituted and unsubstituted aromatic compounds based on a benzene or cyclopentadienyl nucleus, and the anion is tetrafluoroborate, hexafluorophosphate, hexafluoroarsenate, hydroxypentafluoroantimonate, trifluoromethanesulfonate, or hexafluoroantimonate; and

(2) at least one stabilizing additive;

(3) at least one cure rate enhancer;

(d) a plurality of conductive particles; and

(e) optionally, at least one silane coupling agent;

wherein the composition are curable at a temperature of about 120°

-125°

C.

2. The anisotropically conductive adhesive composition according to claim 1 wherein the salt of an organometallic complex cation has the formula:

space="preserve" listing-type="equation">[(L.sup.1).sub.m (L.sup.2).sub.p M].sup.+q X.sub.n

wherein;

M is selected from the group containing Cr, Mo, W, Mn, Re, Fe, Ru, and Os;

L¹ represents a ligand contributing p-electrons that can be selected from substituted and unsubstituted aromatic compounds and substituted or unsubstituted heterocyclic aromatic compounds, and capable of contributing six p-electrons to the valence shell of M;

L² represents a ligand contributing p-electrons that can be selected from substituted or unsubstituted cyclopentadienyl and indenyl anions, and capable of contributing six p-electrons to the valence shell of M;

m and p are integers having a value of 0 or 2, such that, when m is equal to 2, each L¹ may be the same or different ligands and p is equal to 0; and

when p is equal to 2, each L² may be the same or different ligands and m is equal to 0, provided the sum of (m+p) is equal to 2;

q is an integer having a value of 1 or 2, the residual charge of the complex cation;

X is an anion selected from organic sulfonate anions selected from the group consisting of CH₃ SO₃^--, CF₃ SO₃^--, C₆ H₅ SO₃^--, p-toluenesulfonate, p-chlorobenzenesulfonate and related isomers, and halogen-containing complex anions of a metal or metalloid selected from the group consisting of BF₄^--, AsF₆^--, PF₆^--, SbF₅ OH^--, SbF₆^--, and CF₃ SO₃^-- ; and

n is an integer having a value of 1 or 2, the number of complex anions required to neutralize the charge q on the complex cation.

3. The anisotropically conductive adhesive composition according to claim 2 wherein the salt of an organometallic complex cation is bis(η

⁶ -mesitylene)iron(2+) hexafluoroantimonate.

4. The anisotropically conductive adhesive composition according to claim 1 wherein the stabilizing additive has a segment or central nucleus and having a formula selected from the group consisting of:

##STR4## wherein Z² is divalent and can be --O--, --S--, or --NH--;

each R² independently can be hydrogen or R¹ which can be independently selected from C₁ to C₁₀ alkyl groups, or groups of one to four fused or unfused aromatic rings or a divalent radical selected from alkylene (3 to 10 carbon atoms) or phenylene moieties, and further two R² s together can form a cyclic structure of 3 to 10 carbon atoms; and

the carbon atoms can be interrupted with up to 10 individual, non-catenated heteroatoms selected from O, S, and N;

x can be 1 or 2; and

b is an integer from 3 to 10.

5. The anisotropically conductive adhesive composition according to claim 4 wherein the stabilizing additive is a substituted or unsubstituted phenanthroline compound, wherein the substituents are alkyl groups having 1 to 20 carbon atoms.

6. The anisotropically conductive adhesive composition according to claim 5 wherein the stabilizing additive is 1,10-phenanthroline.

7. The anisotropically conductive adhesive composition according to claim 1 wherein the cure rate enhancer is t-amyl oxalate or t-butyl oxalate.

8. The anisotropically conductive adhesive composition according to claim 1 further comprising at least one alcohol-containing material.

9. The anisotropically conductive adhesive composition according to claim 1 further comprising additional adjuvants.

11. The anisotropically conductive adhesive composition according to claim 1 wherein the multi-component thermal initiator is selected from the group consisting of (1) bis(η

⁶ -mesitylene)iron(2+) hexafluoroantimonate, (2) 1,10-phenanthroline; and

(3) one of t-amyl oxalate or t-butyl oxalate.

10. A thermally cationically cured adhesive composition prepared according to the steps of:

(a) providing a thermally cationically curable adhesive composition comprising;

(1) at least one epoxy functional resin;

(2) at least one thermoplastic resin essentially free of nucleophilic or metal complexing functional groups;

(3) a multi-component thermal initiator comprising;

(i) at least one salt of an organometallic complex cation wherein the organometallic cation is selected from a class of substituted or unsubstituted aromatic compounds based on a benzene or cyclopentadienyl nucleus, and the anion is tetrafluoroborate, hexafluorophosphate, hexafluoroarsenate, hydroxypentafluoroantimonate, trifluoromethanesulfonate, or hexafluoroantimonate; and

(ii) at least one stabilizing additive;

(iii) at least one cure rate enhancer;

(4) a plurality of conductive particle'"'"'s; and

(5) optionally, at least one silane coupling agent; and

(b) adding sufficient heat at a temperature of about 120°

-125°

C. to cationically cure the composition.